Ammonia decomposition catalyst and exhaust gas treatment method

Abstract

To provide a catalyst that can promote the gas phase decomposition reaction of NH3 and the gas phase decomposition reaction of NOX and / or N2O while suppressing the by-production of NOX and / or N2O.SOLUTION: A catalyst for gas phase ammonia decomposition comprises: as active catalyst components, a mixture of a first catalyst powder including a support containing at least one selected from the group consisting of ceria, silica, alumina, titania, zirconia, titanosilicate, and aluminosilicate, ruthenium, and platinum supported on the support, and a second catalyst powder including at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate, wherein the amount of platinum relative to 1 pts.mass of ruthenium in the first catalyst powder is 0.001 pts.mass or more and less than 1 pt.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ammonia decomposition catalyst and an exhaust gas treatment method. More specifically, the present invention relates to an ammonia decomposition catalyst and an exhaust gas treatment method. X and / or can promote the gas phase decomposition reaction of ammonia (NH3) while suppressing the by-production of N2O and NO X and / or a catalyst capable of promoting the gas-phase decomposition reaction of NO (a catalyst for gas-phase ammonia decomposition), and NO X and / or decomposes NH3 while suppressing the by-production of N2O and NO X and / or relates to a gas phase reaction process capable of decomposing N2O. [Background technology]

[0002] To achieve carbon neutrality, ammonia fuel, which does not emit carbon dioxide when burned, is expected. When ammonia fuel is burned, NH3, NO X and N2O are emitted. X N2O can have a negative impact on the environment. N2O in particular has a high global warming potential (GWP) of approximately 300, so there is a strong demand to reduce its emissions. Furthermore, in fields where ammonia is stored and utilized, such as ammonia-fueled ships, ammonia transport ships, ammonia fuel storage bases, ammonia tanks for denitration systems in power plants, and ammonia cooling and refrigeration systems, large amounts of gas containing NH3 are released, for example, when tanks and pipes are purged with nitrogen. In the treatment of ammonia-containing wastewater, such as wastewater from food and drinking water production, chemical plants, plating plants, semiconductor component manufacturing, and domestic wastewater, large amounts of gas containing NH3 are released, for example, from diffusion towers. NH3 is a malodorous substance that can cause mucous membrane irritation, respiratory irritation, conjunctival edema, and corrosion.

[0003] NO X Various catalysts and methods have been proposed for promoting the decomposition reaction of nitric oxide (NO) and nitrogen dioxide (NO2) or N2O (nitrous oxide) or for promoting the decomposition reaction of NH3.

[0004] For example, Patent Document 1 discloses an exhaust gas purification catalyst capable of reducing nitrogen oxides to ammonia and oxidatively decomposing ammonia, characterized in that the catalyst comprises a first component that is a composition comprising titanium oxide and oxides of one or more elements selected from molybdenum, tungsten, and vanadium, or a composition comprising zeolite supported with copper or iron, and a second component that is pre-supported on a porous body and that comprises platinum and at least one metal selected from the group consisting of iridium, palladium, rhodium, and ruthenium, with the weight ratio of the metal to the platinum being greater than 0 but not greater than 5. However, Patent Document 1 only specifically discloses in its examples an exhaust gas purification catalyst that combines a first component comprising titanium oxide, tungsten oxide, and vanadium oxide with a second component comprising ruthenium and platinum, and an exhaust gas purification catalyst that combines a first component obtained by ion-exchanging copper ions into mordenite with a second component comprising iridium and platinum.

[0005] Patent Document 2 discloses an exhaust gas aftertreatment device for a diesel engine, comprising a diesel particulate matter filter disposed at the most upstream position on an exhaust pipe connected to an exhaust manifold of the engine, a diesel oxidation catalyst (DOC catalyst) disposed downstream of the diesel particulate matter filter, and an ammonia SCR catalyst containing zeolite disposed downstream of the diesel oxidation catalyst, wherein the diesel oxidation catalyst is comprised of a carrier supporting a single active material made of ruthenium or a carrier supporting a composite active material made of platinum and ruthenium, with the platinum to ruthenium weight ratio being equal to or less than 2. However, Patent Document 2 only discloses the placement of the ammonia SCR catalyst downstream of the diesel oxidation catalyst.

[0006] Patent Document 3 discloses an ammonia slip catalyst including a first SCR catalyst and an oxidation catalyst containing ruthenium or a ruthenium mixture (e.g., a mixture of Pt and Ru) supported on a support including a rutile phase and a substrate. Patent Document 3 discloses that the ammonia slip catalyst contains 0.1 to 10 wt. % ruthenium, and that the term "Pt and Ru mixture" includes a platinum-ruthenium alloy, a Pt-Ru mixed metal oxide, a mixture of discrete Pt and Ru oxide particles on a support, or a combination thereof, in each case with greater than 50 mol. The first SCR catalyst can be, for example, a Cu-SCR catalyst containing copper and a molecular sieve, or an Fe-SCR catalyst containing iron and a molecular sieve. However, Patent Document 3 only specifically discloses an oxidation catalyst containing only ruthenium supported on a support in the examples.

[0007] Patent Document 4 discloses an ammonia decomposition catalyst for treating exhaust gases containing ammonia and moisture, comprising: a first layer containing a precious metal, an inorganic oxide, and a first proton-type zeolite or a first ion-exchanged zeolite ion-exchanged with Cu, Co, or Fe ions; and a second layer provided on the surface of the first layer and containing a second proton-type zeolite or a second ion-exchanged zeolite ion-exchanged with Cu, Co, or Fe ions, wherein the first and second proton-type zeolites and the first and second ion-exchanged zeolites have a CHA structure. Patent Document 4 states that the precious metal is at least one selected from the group consisting of Pt, Pd, Ir, and Rh.

[0008] Patent Document 5 discloses a catalytic device for removing nitrogen oxides and ammonia from the exhaust gas of a lean-burn combustion engine, including an upstream SCR catalyst including a support substrate and a first washcoat containing a first SCR catalytically active composition applied to the support substrate, and a downstream ASC catalyst including a support substrate and a lower layer including a third washcoat containing an oxidation catalyst applied to the support substrate, and an upper layer including a second washcoat containing a second SCR catalytically active composition applied to the lower layer. Patent Document 5 teaches that the oxidation catalyst includes a platinum group metal selected from the group consisting of ruthenium, rhodium, palladium, iridium, and platinum.

[0009] Furthermore, as a catalyst for treating wastewater containing nitrogen compounds such as ammonia, for example, Patent Document 6 discloses a catalyst for use in wet oxidation treatment of wastewater, which is characterized in that it comprises ruthenium, a compound containing at least one element selected from the group consisting of iron, titanium, silicon, aluminum, zirconium, and cerium as component A, and at least one noble metal selected from the group consisting of silver, gold, platinum, palladium, and iridium as component B or a compound containing said noble metal, and the mass ratio of ruthenium to component B (Ru / B ratio) is 2 / 1 or more and 50 / 1 or less. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 8-290062 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-52679 [Patent Document 3] WO 2018 / 057844 A1 [Patent Document 4] Japanese Patent Publication No. 2022-105849 [Patent Document 5] Special Publication No. 2024-500370 [Patent Document 6] JP 2014-140800 A Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to X and / or can promote the gas phase decomposition reaction of ammonia (NH3) while suppressing the by-production of N2O and NO X and / or a catalyst capable of promoting the gas-phase decomposition reaction of NO (a catalyst for gas-phase ammonia decomposition), and NO X and / or decomposes NH3 while suppressing the by-production of N2O and NO X and / or to provide a gas phase reaction process capable of decomposing N2O. [Means for solving the problem]

[0012] [1] A first catalyst powder comprising a support containing at least one selected from the group consisting of ceria, silica, alumina, titania, zirconia, titanosilicate, and aluminosilicate, and ruthenium and platinum supported on the support; a second catalyst powder containing at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; as an active catalyst component, and The first catalyst powder has a platinum content of 0.001 parts by mass or more and less than 1 part by mass per part by mass of ruthenium. Catalyst for gas-phase ammonia decomposition.

[0013] [2] The catalyst according to [1], wherein the first catalyst powder contains 0.01 parts by mass or more and less than 0.5 parts by mass of platinum per 1 part by mass of ruthenium, the amount of platinum contained in 100 parts by mass of the first catalyst powder is 0.01 to 2 parts by mass, and the amount of ruthenium contained in 100 parts by mass of the first catalyst powder is 2 to 10 parts by mass.

[0014] [3] The catalyst according to [1], wherein the first catalyst powder contains platinum in an amount of 0.01 parts by mass or more but less than 0.5 parts by mass per part by mass of ruthenium, the amount of platinum contained in a total of 100 parts by mass of the first catalyst powder and the second catalyst powder is 0.001 to 0.1 parts by mass, and the amount of ruthenium contained in a total of 100 parts by mass of the first catalyst powder and the second catalyst powder is 0.01 to 1 part by mass.

[0015] [4] The catalyst according to any one of [1] to [3], wherein the first catalyst powder has a support containing at least one selected from the group consisting of silica, titanosilicate, MEL-type aluminosilicate, and MFI-type aluminosilicate.

[0016] [5] The catalyst according to any one of [1] to [4], wherein the second catalyst powder contains an iron ion-exchanged BEA-type aluminosilicate.

[0017] [6] The catalyst according to any one of [1] to [5], wherein the second catalyst powder comprises an iron ion-exchanged, OSDA-free, BEA-type aluminosilicate.

[0018] [7] A catalyst for gas-phase ammonia decomposition, comprising a support and the catalyst according to any one of [1] to [6] supported on the support. [8] A catalyst body for gas-phase ammonia decomposition, comprising a molded body containing the catalyst according to any one of [1] to [6].

[0019] [9] In the presence of the catalyst according to any one of [1] to [6], in a gas to be treated, The chemical reaction that turns NH3 into nitrogen and water, NO X and the chemical reaction that turns N2O into nitrogen and water. A process that includes:

[0020]

[10] The gas to be treated is continuously passing the second catalyst powder through a first catalyst layer containing, as an active catalyst component, only a second catalyst powder comprising at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; Subsequently, the mixture is continuously passed through a second catalyst layer containing the catalyst according to any one of [1] to [6]. In the gas to be treated, a chemical reaction occurs that converts NH3 into nitrogen and water, and NO X and a process for chemically reacting N2O to nitrogen and water.

[0021]

[11] The gas to be treated is [1] to [6] are continuously passed through a first catalyst layer containing the catalyst; Subsequently, the mixture is continuously passed through a second catalyst layer containing the catalyst according to any one of [1] to [6]; The proportion of platinum contained in the catalyst placed in the first catalyst layer is lower than the proportion of platinum contained in the catalyst placed in the second catalyst layer. In the gas to be treated, a chemical reaction occurs that converts NH3 into nitrogen and water, and NO X and a process for chemically reacting N2O to nitrogen and water.

[0022]

[12] The process according to [9],

[10] or

[11] , further comprising adding at least one reaction aid selected from the group consisting of ammonia and urea to the gas to be treated.

[0023]

[13] A first catalyst layer comprising a catalyst containing, as an active catalyst component, only a second catalyst powder containing at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; and a second catalyst layer disposed downstream of the first catalyst layer and comprising the catalyst according to any one of [1] to [6]. Apparatus for gas phase ammonia decomposition.

[0024]

[14] A first catalyst layer comprising the catalyst according to any one of [1] to [6]; A second catalyst layer comprising the catalyst according to any one of [1] to [6], which is disposed downstream of the first catalyst layer; and The proportion of platinum contained in the catalyst placed in the first catalyst layer is lower than the proportion of platinum contained in the catalyst placed in the second catalyst layer. Apparatus for gas phase ammonia decomposition. [Effects of the Invention]

[0025] The catalyst of the present invention is X The catalyst of the present invention has the function of reducing NO and nitrous oxide (NO) to ammonia and the function of oxidizing and decomposing ammonia (NH). X and / or can promote the gas phase decomposition reaction of ammonia (NH3) while suppressing the by-production of N2O and NO X The catalyst of the present invention can convert a gas containing NH3 into a gas containing NH3 with a low NH3 concentration and a low NO concentration. X The N2O gas is suitable for chemical reactions to convert it into a gas with high and / or low N2O concentrations. The process of the present invention is X and / or decomposes ammonia (NH3) while suppressing the by-production of N2O and produces NO X The process of the present invention can decompose NH3-containing gases into gases with low NH3 concentrations, low NO and / or NO. X It is suitable for converting N2O into a gas with high and / or low N2O concentration.

[0026] The chemical reaction that can directly convert NH3 into nitrogen and water (direct decomposition reaction of ammonia) is represented by equation (4). 4NH3 + 3O2 → 2N2 + 6H2O (4)

[0027] NO X into nitrogen and water (NO XThe vapor-phase decomposition reactions of methyl methyl ketone (Methyl ketone) are expressed by the following equations (6), (7), and (8): 4NO + 4NH3+ O2→ 4N2+ 6H2O (6) 6NO2 + 8NH3 → 7N2 + 12H2O (7) NO + NO2+ 2NH3→ 2N2+ 3H2O (8) The chemical reaction that can convert N2O into nitrogen and water (gas-phase decomposition reaction of N2O) is expressed by equation (9). 3N2O + 2NH3 → 4N2 + 3H2O (9)

[0028] In parallel with the chemical reaction represented by formula (4), the chemical reactions (side reactions) represented by formulas (1), (2), and (3) may proceed. 4NH3 + 5O2 → 4NO + 6H2O (1) 4NH3 + 7O2 → 4NO2 + 6H2O (2) 2NH3 + 2O2 → N2O + 3H2O (3) NO X and N2O are harmful substances that affect the environment, etc. As described above, the catalyst of the present invention promotes a chemical reaction (direct decomposition reaction of ammonia) that can directly convert NH3 into nitrogen and water, so NO X The catalyst of the present invention reduces the rate of reaction (side reaction) that produces NO and N2O as a by-product. X As a result, the catalyst of the present invention can convert NH3 into an intermediate (NO X This promotes a chemical reaction (indirect decomposition of ammonia) that can convert ammonia into nitrogen and water via NH3 and NO. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a graph showing the relationship between the NOx by-production rate @ 500°C and the NH3 decomposition reaction rate @ 350°C, which is the result of evaluation (1). [Figure 2] FIG. 1 is a graph showing the relationship between the N2O by-production rate @ 350°C and the NH3 decomposition reaction rate @ 350°C, which is the result of evaluation (1). [Figure 3] FIG. 1 is a graph showing the relationship between the NOx by-production rate @500°C, which is the result of evaluation (1), and the NH3 decomposition reaction rate aging rate @350°C, which are the results of evaluation (1) and evaluation (2). [Figure 4] FIG. 1 is a graph showing the relationship between the N2O by-production rate @ 350°C, which is the result of evaluation (1), and the NH3 decomposition reaction rate aging rate @ 350°C, which is the result of evaluation (1) and evaluation (2). [Figure 5] FIG. 10 is a graph showing the relationship between the NOx by-production rate @ 500°C and the NH3 decomposition reaction rate @ 350°C, which is the result of evaluation (2). [Figure 6] FIG. 10 is a graph showing the relationship between the N2O by-production rate @ 350°C and the NH3 decomposition reaction rate @ 350°C, which is the result of evaluation (2). [Figure 7] FIG. 10 is a graph showing the relationship between the NOx by-production rate @500°C, which is the result of evaluation (2), and the NH3 decomposition reaction rate aging rate @350°C, which is the result of evaluation (1) and evaluation (2). [Figure 8] FIG. 10 is a graph showing the relationship between the N2O by-production rate @ 350°C, which is the result of evaluation (2), and the NH3 decomposition reaction rate aging rate @ 350°C, which is the result of evaluation (1) and evaluation (2). DETAILED DESCRIPTION OF THE INVENTION

[0030] The catalyst for vapor phase ammonia decomposition of the present invention comprises a mixture of a first catalyst powder and a second catalyst powder as an active catalyst component.

[0031] The first catalyst powder comprises a support and ruthenium and platinum supported on the support.

[0032] The support used in the first catalyst powder is a support containing at least one selected from the group consisting of ceria, silica, alumina, titania, zirconia, titanosilicate, and aluminosilicate. The support used in the first catalyst powder is preferably a support containing silica, alumina, and / or titania, more preferably a support containing silica, titanosilicate, or aluminosilicate. The support used in the first catalyst powder is preferably porous. The specific surface area of ​​the support used in the first catalyst powder is not particularly limited, and may be, for example, 10 to 1000 m. 2 / g is preferred, and 50 to 500m 2 Specific examples of the carrier used in the first catalyst powder include ceria powder, silica powder, alumina powder, titania powder, zirconia powder, titanosilicate powder, and aluminosilicate powder; a mixture of two or more powders selected from the group consisting of ceria powder, silica powder, alumina powder, titania powder, zirconia powder, titanosilicate powder, and aluminosilicate powder; powder of a composite of two or more oxides selected from the group consisting of ceria, silica, alumina, titania, zirconia, titanosilicate, and aluminosilicate (e.g., silica-titania, alumina-titania, ceria-titania, silica-alumina, silica-zirconia, alumina-zirconia, etc.); Examples include powders in which at least one powder selected from the group consisting of ceria powder, silica powder, alumina powder, titania powder, zirconia powder, titanosilicate powder, and aluminosilicate powder is doped, supported, or composited with at least one element selected from the group consisting of cerium, silicon, aluminum, titanium, and zirconium and different from the elements constituting the powder, and / or other metal elements such as molybdenum, tungsten, and vanadium. Doped, supported, or composited powders tend to have high resistance to hydrothermal aging.

[0033] Titanosilicates are composites of titania and silica, and aluminosilicates are composites of alumina and silica. Silica, titanosilicate, or aluminosilicate may be a hydrous oxide, a hydrated oxide, or an anhydrous oxide. The support used in the first catalyst powder is preferably crystalline and porous. Silica and aluminosilicate may have a structure formed by stacking SiO4 tetrahedron sheets (a structure in which SiO4 tetrahedrons are two-dimensionally connected via oxygen atoms, a layered structure), but preferably have a zeolite structure or a structure in which SiO4 tetrahedrons are three-dimensionally connected via oxygen atoms. Titanosilicate may be a composite structure in which titania is coated with silica, or a composite structure in which silica is coated with titania. The titanosilicate preferably used in the present invention has a titania / silica ratio of preferably 0.1 / 99.9 to 99.9 / 0.1, more preferably 50 / 50 to 99.5 / 0.5, and even more preferably 70 / 30 to 99 / 1.

[0034] Examples of the structure of the aluminosilicate used in the first catalyst powder include A-type (LTA-type), X-type (FAU-type), LSX-type (FAU-type), beta-type (BEA-type), ZSM-5-type (MFI-type), ZSM-11-type (MEL-type), ferrierite-type (FER-type), mordenite-type (MOR-type), L-type (LTL-type), Y-type (FAU-type), MCM-22-type (MWW-type), offretite / erionite-type (O / E-type), AEI-type, AEL-type, AFT-type, AFX-type, CHA-type, EAB-type, ERI-type, KFI-type, LEV-type, LTN-type, MSO-type, RHO-type, SAS-type, SAT-type, SAV-type, SFW-type, TON-type, and TSC-type. Of these, MFI-type or MEL-type is preferred, and MFI-type is more preferred.

[0035] The first catalyst powder has ruthenium and platinum supported on a carrier, and the amount of platinum (Pt) per part by mass of ruthenium (Ru) in the first catalyst powder is 0.001 to less than 1 part by mass, more preferably 0.005 to less than 0.8 parts by mass, even more preferably 0.01 to less than 0.5 parts by mass, still more preferably 0.03 to 0.3 parts by mass, and even more preferably 0.015 to 0.25 parts by mass.

[0036] In the first catalyst powder, the amount of platinum (Pt) contained in 100 parts by mass of the first catalyst powder is preferably 0.01 to 2 parts by mass, more preferably 0.05 to 1.5 parts by mass, and even more preferably 0.01 to 1.2 parts by mass.

[0037] In the first catalyst powder, the amount of ruthenium (Ru) contained in 100 parts by mass of the first catalyst powder is preferably 2 to 10 parts by mass, more preferably 3 to 8 parts by mass, and even more preferably 4 to 6 parts by mass.

[0038] The first catalyst powder may have a metal element other than ruthenium and platinum supported on a carrier. Examples of such metal elements include gold, silver, rhodium, palladium, osmium, iridium, and rhenium; rare earth elements such as cerium (Ce); and rare metal elements such as molybdenum, tungsten, and vanadium. The ratio of the rare earth element to the carrier in the first catalyst powder is not particularly limited as long as it does not impair the effects of the present invention. For example, the amount of the rare earth element per 1 part by mass of the total amount of ruthenium and platinum in the first catalyst powder is preferably 1 part by mass or more but less than 10 parts by mass, more preferably 3 parts by mass or more but 7 parts by mass or less, and even more preferably 4 parts by mass or more but 6 parts by mass or less. First catalyst powders in which a metal element other than ruthenium and platinum is supported on a carrier tend to have high resistance to hydrothermal aging (high aging ratio).

[0039] Preparation of the first catalyst powder involves, for example, supporting ruthenium and platinum on a support, followed by pulverization or crushing as necessary. Supporting can be performed, for example, by immersing the support in a solution, suspension, or emulsion containing ruthenium and platinum. Supporting of metal elements other than ruthenium and platinum can also be performed in a similar manner. After immersion, kneading, evaporation to dryness, drying, calcination, etc. can be performed. The drying temperature may be any temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature may be any temperature below the heat resistance temperature of the support, for example, 350 to 550°C. The calcination time is, for example, 1 to 5 hours.

[0040] The first catalyst powder is preferably porous. The pore size distribution of the first catalyst powder is not particularly limited. The first catalyst powder is not particularly limited by its particle size distribution as long as it is in the form of a fine powder. The particle size distribution can be adjusted by pulverization / crushing, classification, etc.

[0041] The second catalyst powder comprises at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate.

[0042] The iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, or copper ion-exchanged BEA-type aluminosilicate is obtained by exchanging some or all of the cations in the BEA-type aluminosilicate with iron ions, cobalt ions, or copper ions.

[0043] The BEA-type aluminosilicates that can be subjected to ion exchange have a Si / Al ratio in skeletal analysis. 骨格 but preferably not less than 9. The higher the proportion of Si, the higher the durability of the catalyst tends to be. 29 The spectrum measured by Si MAS NMR is (SiO4) 4-Depending on the number n of four TO4 atoms adjacent to the , where T is Al, resonance absorptions of Si(0Al), Si(1Al), Si(2Al), Si(3Al) and Si(4Al) are observed. Their peak intensities I Si(nAl) from Si / Al 骨格 is calculated by a known method. The BEA-type aluminosilicate that can be subjected to ion exchange is preferably porous. The pore size of the BEA-type aluminosilicate that can be subjected to ion exchange is not particularly limited, and is, for example, preferably 0.01 to 10 nm, more preferably 0.2 to 2 nm. The specific surface area of ​​the BEA-type aluminosilicate that can be subjected to ion exchange is not particularly limited, and is, for example, 100 to 1200 m 2 / g is preferred, and 200 to 800m 2 / g is more preferred.

[0044] BEA-type aluminosilicates can be obtained by, for example, mixing a silica source, an alumina source, an alkali source, a solvent, an organic structure-directing agent (OSDA), a surfactant, etc. to obtain a starting reaction mixture, which is then subjected to a hydrothermal reaction under high temperature and pressure in an autoclave. The BEA-type aluminosilicate obtained by this method contains organic components derived from the OSDA. However, it appears that the organic components can be removed by subsequent calcination.

[0045] BEA-type aluminosilicate can be obtained by hydrothermal reaction without using OSDA. BEA-type aluminosilicate can be obtained by utilizing mechanochemical treatment and steam synthesis without using OSDA. BEA-type aluminosilicate obtained without using OSDA (hereinafter sometimes referred to as OSDA-free BEA-type aluminosilicate) does not contain organic components derived from OSDA. In the present invention, OSDA-free BEA-type aluminosilicate can be preferably subjected to ion exchange.

[0046] Ion exchange can be carried out by immersing a BEA-type aluminosilicate or an OSDA-free BEA-type aluminosilicate in a solution containing iron ions, cobalt ions, or copper ions, followed by filtration, drying, and calcination as necessary. The pH of the solution containing iron ions, cobalt ions, or copper ions is preferably adjusted appropriately to promote ion exchange. The pH of the solution containing iron ions, cobalt ions, or copper ions is, for example, 1 to 8, preferably 1.2 to 6, and more preferably 1.5 to 5. To adjust the pH, basic compounds such as sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, sodium carbonate, or potassium carbonate, or acidic compounds such as hydrochloric acid or nitric acid, can be used. The drying temperature may be any temperature at which the liquid can be removed, for example, 100 to 150°C. The firing temperature may be any temperature lower than the heat resistance temperature of the BEA-type aluminosilicate or OSDA-free BEA-type aluminosilicate, for example, 350 to 800°C. The firing time may be appropriately set depending on the firing temperature, for example, 1 to 10 hours. After ion exchange, the product can be powdered by pulverization or crushing, as needed. The amount of iron ions, cobalt ions or copper ions exchanged for cations is preferably 0.1 to 10 mass %, more preferably 0.7 to 7 mass %, based on the BEA-type aluminosilicate or OSDA-free BEA-type aluminosilicate. The second catalyst powder may contain at least one element selected from the group consisting of Fe, Co, and Cu attached (supported) to a BEA-type aluminosilicate or an OSDA-free BEA-type aluminosilicate.

[0047] The second catalyst powder is preferably porous. The pore size distribution of the second catalyst powder is not particularly limited. The second catalyst powder is not particularly limited by the particle size distribution as long as it is in the form of a fine powder. The particle size distribution can be adjusted by pulverization / crushing, classification, etc. The second catalyst powder may be Si / Al 骨格 The second catalyst powder preferably has a Si / Al ratio of 9 or more before and after ion exchange.骨格 It is preferable that the value has not changed.

[0048] The second catalyst powder has acid sites derived from OH groups and the like. The properties of the acid sites can be observed using a method commonly known as the pyridine-TPD method. For example, a flame ionization detector (FID) can be used as a detector in the pyridine-TPD method. Pyridine adsorbs to the acid sites. Pyridine can adsorb to both the acid sites on the outer surface of the catalyst pores and the acid sites on the inner surface of the pores. It is generally understood that the higher the temperature at which the adsorbed pyridine desorbs, the stronger the acid strength of the acid sites. It has also been suggested that pyridine desorbed at high temperatures originates from acid sites affected by diffusion, i.e., acid sites on the inner surface of the pores (Nakano et al., "Measurement of the Acidity of Zeolites by Temperature-Programmed Desorption Method," Toyo Soda Research Report, Vol. 29, No. 1 (1985), pp. 3-11). The effective molecular diameter of pyridine is said to be 5.8 Å (see Anderson et al., J. Catal., 58, 114 (1979)). The total number of acid sites can be determined from the saturated adsorption amount of pyridine. After adsorbing pyridine, the temperature is raised at a constant rate (20°C / min). The distribution of the amount of pyridine desorbed at each temperature (this distribution is sometimes referred to as a TPD spectrum) can be used to determine the acid strength distribution of the acid sites. In the present invention, pyridine adsorption can be performed at room temperature to 150°C, preferably at 150°C.

[0049] In the TPD spectrum of the second catalyst powder, the ratio of the total amount of pyridines eliminated within a temperature range of 150° C. or higher and lower than 450° C. to the total amount of pyridines eliminated within a temperature range of 450° C. or higher and 800° C. is preferably 0.9 or higher, more preferably 0.98 or higher, even more preferably 1 or higher, and still more preferably 1.1 or higher. There is no particular upper limit to the ratio of the total amount of pyridines eliminated within a temperature range of 150° C. or higher and lower than 450° C. to the total amount of pyridines eliminated within a temperature range of 450° C. or higher and 800° C., as long as the powder can be produced.

[0050] In the second catalyst powder, the total amount of pyridine eliminated within a temperature range of 150° C. or higher and lower than 450° C. in a TPD spectrum is preferably 100 μmol or more, more preferably 200 μmol or more, even more preferably 250 μmol or more, and still more preferably 300 μmol or more per gram of catalyst. There is no particular upper limit to the total amount of pyridine eliminated within a temperature range of 150° C. or higher and lower than 450° C., as long as it can be produced.

[0051] In the second catalyst powder, the total amount of pyridine eliminated within the temperature range of 450° C. to 800° C. in TPD spectrum is preferably 1000 μmol or less, more preferably 800 μmol or less, and even more preferably 500 μmol or less per gram of catalyst. The lower limit of the total amount of pyridine eliminated within the temperature range of 450° C. to 800° C. is not particularly limited, as long as it can be produced.

[0052] In the TPD spectrum of the second catalyst powder, the L peak value (the amount of pyridine desorption at the maximum peak top located in the range of 150°C or higher but lower than 450°C) is greater than the H peak value (the amount of pyridine desorption at the maximum peak top located in the range of 450°C or higher but lower than 800°C). That is, the ratio of the L peak value to the H peak value is preferably greater than 1, more preferably 1.12 or higher, even more preferably 1.2 or higher, still more preferably 1.4 or higher, and most preferably 1.6 or higher. There is no particular upper limit to the ratio of the L peak value to the H peak value, as long as it is producible.

[0053] The second catalyst powder has a lower limit of the temperature at which the H peak appears in the TPD spectrum (the temperature at the maximum peak top within the range of 450°C or higher and 800°C or lower) of preferably 490°C, more preferably 510°C, and even more preferably 530°C, and an upper limit of 650°C, more preferably 620°C, even more preferably 600°C, and even more preferably 580°C.

[0054] The second catalyst powder preferably has a high saturated adsorption amount of pyridine. The saturated adsorption amount of pyridine in the second catalyst powder is preferably 100 μmol or more, more preferably 200 μmol or more, even more preferably 500 μmol or more, and even more preferably 700 μmol or more per gram of catalyst. The upper limit of the saturated adsorption amount of pyridine in the second catalyst powder is not particularly limited as long as it can be produced, and is, for example, preferably 2000 μmol, more preferably 1500 μmol per gram of catalyst. The saturated adsorption amount of pyridine can be measured at 150°C.

[0055] The second catalyst powder preferably has a large crystallite size. The crystallite size of the second catalyst powder is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 20 nm or more, and even more preferably 30 nm or more. The upper limit of the crystallite size of the second catalyst powder is not particularly limited as long as it can be produced, and is, for example, preferably 100 nm, more preferably 80 nm. The crystallite size can be measured by X-ray diffraction (see, for example, JIS H 7805 or JIS R 7651).

[0056] The second catalyst powder preferably has high NO decomposition rates and NO decomposition rates even after being exposed to gas containing 20% ​​H2O and 20 ppm SO2 at 530°C for 70 hours.The second catalyst powder preferably has an NO decomposition rate of 60% or more and an NO decomposition rate of 90% or more at 450°C even after being exposed to gas containing 20% ​​H2O and 20 ppm SO2 at 530°C for 70 hours.

[0057] The catalyst for vapor phase ammonia decomposition of the present invention may contain a third catalyst powder as an active catalyst component in addition to the first catalyst powder and the second catalyst powder.

[0058] The third catalyst powder comprises an oxide of titanium, an oxide of tungsten and / or molybdenum, and an oxide of cerium and / or vanadium, preferably an oxide of titanium, an oxide of tungsten, and an oxide of cerium.

[0059] The ratio of Ce element and / or V element to Ti element is preferably 1 to 20% by weight, more preferably 3 to 15% by weight, as a weight percentage of (CeO2+V2O5) / TiO2. The ratio of Mo element and / or W element to Ti element is preferably 1 to 50 wt %, more preferably 10 to 40 wt %, in terms of weight percentage of (MoO3+WO3) / TiO2.

[0060] In preparing the third catalyst powder, titanium oxide powder or a titanium oxide precursor can be used as the titanium oxide raw material. Examples of titanium oxide precursors include titanium oxide slurry, titanium oxide sol, titanium sulfate, titanium tetrachloride, titanates, and titanium alkoxides. In the present invention, a material that forms anatase titanium oxide is preferably used as the titanium oxide raw material. Vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate can be used as the vanadium oxide raw material. Ammonium paratungstate, ammonium metatungstate, tungsten trioxide, and tungsten chloride can be used as the tungsten oxide raw material. Ammonium molybdate and molybdenum trioxide can be used as the molybdenum oxide raw material. Cerium oxide raw materials include cerous nitrate, ceric nitrate, cerium carbonate, cerous sulfate, ceric sulfate, and cerous acetate.

[0061] The third catalyst powder may contain, as a promoter or additive, an oxide of P, an oxide of S, an oxide of Al (e.g., alumina), an oxide of Si (e.g., glass fiber), an oxide of Zr (e.g., zirconia), gypsum (e.g., gypsum dihydrate), zeolite, etc. These can be used in the form of powder, sol, slurry, fiber, etc. when preparing the catalyst.

[0062] The preparation of the third catalyst powder includes, for example, adding a solvent (e.g., water) to the raw materials of each oxide and, if necessary, a co-catalyst or additive, kneading the mixture, evaporating to dryness, drying, calcining the resulting mixture, and then, if necessary, pulverizing or crushing it to obtain a powder. The drying temperature may be any temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature may be any temperature below the heat resistance temperature of the oxide, for example, 350 to 550°C. The calcination time is, for example, 1 to 5 hours.

[0063] The third catalyst powder is preferably porous. The pore size distribution of the third catalyst powder is not particularly limited. The third catalyst powder is not particularly limited by its particle size distribution as long as it is in the form of a fine powder. The particle size distribution can be adjusted by pulverization / crushing, classification, etc.

[0064] The mixture contained in the catalyst of the present invention can be obtained by mixing a first catalyst powder, a second catalyst powder, and, if necessary, a third catalyst powder. The mixing may be dry or wet mixing. After mixing, drying or calcination, pulverization / crushing, granulation, and classification may be performed as needed. The drying temperature may be any temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature may be any temperature lower than the heat resistance temperature of the oxide, for example, preferably 350 to 650°C, more preferably 450 to 600°C, and even more preferably 480 to 570°C. The calcination time can be appropriately set depending on the calcination temperature, for example, 1 to 5 hours. The catalyst of the present invention is not particularly limited by particle size distribution. The particle size distribution can be adjusted by pulverization / crushing, granulation, classification, etc.

[0065] The mixing ratio of the first catalyst powder to the second catalyst powder or the mixing ratio of the first catalyst powder to the second catalyst powder to the third catalyst powder is determined based on, for example, the concentration of NH3, NO in the gas flowing out from the catalyst layer or the reactor. X The concentration and N2O concentration can be set so that they are within predetermined ranges.

[0066] The amount of the first catalyst powder contained in the catalyst of the present invention is preferably 0.01 to 10 mass %, more preferably 0.1 to 5 mass %, and even more preferably 0.5 to 3 mass %. The amount of the second catalyst powder relative to 1 part by mass of the first catalyst powder is preferably 1 to 100 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 20 to 55 parts by mass.

[0067] In the catalyst of the present invention, the amount of platinum contained in 100 parts by mass of the total of the first catalyst powder and the second catalyst powder is preferably 0.0005 to 0.2 parts by mass, and more preferably 0.001 to 0.1 parts by mass. In the catalyst of the present invention, the amount of ruthenium contained in 100 parts by mass of the total amount of the first catalyst powder and the second catalyst powder is preferably 0.01 to 1 part by mass, more preferably 0.05 to 0.5 parts by mass. The total amount of ruthenium and platinum contained in the catalyst of the present invention is preferably 1 to 5000 ppm, more preferably 10 to 3000 ppm, even more preferably 100 to 2000 ppm, and even more preferably 250 to 1800 ppm.

[0068] The third catalyst powder can be mixed when heat resistance is required. The amount of the third catalyst powder per part by mass of the first catalyst powder is preferably 0 to 70 parts by mass, more preferably 0 to 50 parts by mass, and even more preferably 0 to 30 parts by mass. As the proportion of the third catalyst powder increases, the outlet NH3 concentration can be reduced during reactions at high temperatures, such as 500°C or higher.

[0069] In the present invention, the catalyst of the present invention may be attached (supported) on a support to form a catalyst body for gas-phase ammonia decomposition, or a molded article obtained by molding the catalyst of the present invention may be used as a catalyst body for gas-phase ammonia decomposition. Examples of the support include honeycomb supports, corrugated supports, and plate-like supports (lath plates) such as expanded metal and perforated metal (punched metal). The amount of catalyst attached to the support can be appropriately set, taking into consideration the improvement of the catalyst loading rate, etc. The molded body may have a shape such as honeycomb, corrugated, cone, truncated cone, ellipsoid, spindle, Raschig ring, Dixon, saddle, or McMahon, taking into consideration an improvement in catalyst loading rate and suppression of an increase in head loss.

[0070] When producing the catalyst body, the catalyst of the present invention may contain an amorphous metal oxide such as amorphous silica, amorphous alumina, or amorphous titania as an additive.

[0071] After being supported on the support or formed, the mixture can be dried or calcined as necessary. The drying temperature may be any temperature at which the liquid can be removed, for example, 100 to 150°C. The calcination temperature may be any temperature lower than the heat resistance temperature of the mixture, for example, preferably 350 to 650°C, more preferably 450 to 600°C, and even more preferably 480 to 570°C. The calcination time can be set appropriately depending on the calcination temperature, for example, 1 to 5 hours.

[0072] The process of the present invention involves a chemical reaction in the presence of the catalyst of the present invention to convert NH3 into nitrogen and water in the treated gas, and a reaction to convert NO X and a chemical reaction that converts N2O into nitrogen and water. X As will be described later, N2O may be those originally contained in the gas to be treated, or may be those generated during the chemical reaction.

[0073] The gas to be treated contains NH3-containing gas. Examples of NH3-containing gas include exhaust gas generated by the combustion of ammonia fuel, exhaust gas released during purging of ammonia-related facilities, and exhaust gas released during the treatment of ammonia-containing wastewater. Examples of NH3-containing gas include gases emitted from ammonia-fueled ships, ammonia transport ships, ammonia fuel storage bases, ammonia tanks for denitration systems in power plants, ammonia cooling and refrigeration systems, and other ammonia-containing wastewater treatment plants, such as food and drinking water production wastewater, chemical plant wastewater, plating wastewater, semiconductor component manufacturing wastewater, and domestic wastewater. When NH3 is dissolved in a liquid or adsorbed on a solid, it can be vaporized using a stripper tower, vaporizer, or the like.

[0074] The gas to be treated preferably further contains an O2-containing gas. For example, the air can be used as the O2-containing gas. For example, if the O2 concentration in the NH3-containing gas is at a level sufficient to carry out the chemical reaction, the NH3-containing gas can be used as is as the gas to be treated. If not, a gas obtained by mixing the NH3-containing gas and the O2-containing gas can be used as the gas to be treated.

[0075] The mass ratio of O2 to NH3 can be determined by, for example, the concentration of NH3, NO2, and the like in the gas obtained by the chemical reaction (hereinafter, sometimes referred to as the treated gas). X The concentration and N2O concentration can be appropriately set so that they are within the desired ranges. The exhaust gas produced by burning ammonia fuel is NO X or / and N2O. The gas to be treated contains NO X Or / and N2O may be further included.

[0076] The chemical reaction in the process of the present invention is preferably carried out in a continuous flow reactor. A catalyst bed is installed in the reactor, and the catalyst is placed in the catalyst bed. The catalyst bed can be in the form of a fixed bed, fluidized bed, moving bed, simulated moving bed, etc., preferably in the form of a fixed bed or simulated moving bed. In the continuous flow reactor, gas adjusted to a predetermined temperature is introduced into the reactor inlet, where it undergoes a chemical reaction in the catalyst layer inside the reactor, and the gas is discharged from the reactor outlet. The space velocity of the gas flowing through the reactor [1 / hr] (= volumetric flow rate (m 3 / hr) / catalyst volume (m 3 )) is, for example, the NH3 concentration, NO concentration in the gas flowing out from the catalyst layer or reactor. X The gas temperature at the reactor inlet is, for example, preferably 300 to 600°C, more preferably 350 to 550°C.

[0077] A preferred embodiment of the process of the present invention is a process in which NH3 is converted into nitrogen and water in the gas to be treated, and NO X and a chemical reaction of converting NO into nitrogen and water, the method includes, for example, continuously passing the gas to be treated through a first catalyst layer containing, as an active catalyst component, only a second catalyst powder containing at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate, and then continuously passing the gas to be treated through a second catalyst layer containing the catalyst of the present invention. Another preferred embodiment of the process of the present invention is a process in which NH3 is converted into nitrogen and water in the gas to be treated by a chemical reaction, and NO X and a chemical reaction that converts N2O into nitrogen and water, the method includes, for example, continuously passing the gas to be treated through a first catalyst layer containing the catalyst of the present invention, and then continuously passing the gas to be treated through a second catalyst layer containing the catalyst of the present invention, wherein the proportion of platinum contained in the catalyst placed in the first catalyst layer is lower than the proportion of platinum contained in the catalyst placed in the second catalyst layer.

[0078] In the catalyst layer (second catalyst layer) where the catalyst of the present invention is placed, NO X The gas-phase decomposition reaction of NO (reaction represented by formula (6), formula (7), or formula (8)), the gas-phase decomposition reaction of NO (reaction represented by formula (9)), and the direct decomposition reaction of NH (reaction represented by formula (4)) are promoted in a balanced manner, while the side reaction that produces NO (reaction represented by formula (3)) is suppressed. The higher the temperature, the more the gas-phase decomposition reaction of NO and the direct decomposition reaction of NH tend to be promoted.

[0079] In the first catalyst layer, NO X The gas-phase decomposition reaction of NO (reaction represented by formula (6), formula (7), or formula (8)) is mainly promoted, and the gas-phase decomposition reaction of NO (reaction represented by formula (9)) is also promoted. X The gas-phase decomposition reaction of N2O and the gas-phase decomposition reaction of N2O tend to be promoted.

[0080] NO promoted in the first catalyst layer X The gas-phase decomposition reaction of NO generates a large amount of heat. As a result, the gas flowing out from the first catalytic layer tends to be at a higher temperature than the gas flowing into the first catalytic layer. The higher the temperature of the gas flowing into the catalytic layer (second catalytic layer) using the catalyst of the present invention, the higher the temperature of the catalytic layer (second catalytic layer) using the catalyst of the present invention, so the gas-phase decomposition reaction of NO and the direct decomposition reaction of NH tend to be promoted. The direct decomposition reaction of NH promoted in the catalytic layer (second catalytic layer) using the catalyst of the present invention also generates additional heat. As a result, even in a gas to be treated with a high ammonia concentration, the process of the present invention using the first catalytic layer and the second catalytic layer can efficiently decompose NH and produce a treated gas with a low NO emission concentration.

[0081] NO promoted in the first catalyst layer XNH3 is also consumed in the gas-phase decomposition reaction of NO and the gas-phase decomposition reaction of NO. When NH3 is consumed in the first catalytic layer and the amount of ammonia contained in the gas flowing into the catalytic layer (second catalytic layer) using the catalyst of the present invention is small, the progress of the side reaction (reaction represented by formula (3) or the like) that produces NO is suppressed. As a result, even if the treated gas has a low ammonia concentration, the process of the present invention using the first catalytic layer and the second catalytic layer significantly reduces the NO concentration in the treated gas.

[0082] As described above, the process of the present invention using the first and second catalyst layers can handle gases with a wide range of ammonia concentrations, from low to high. For example, in an NH3-fueled marine engine, the amounts of NOx, NO, and NH3 contained in the exhaust gas can vary significantly depending on the engine load. By applying the process of the present invention to exhaust gases with such concentration fluctuations, NH3 can be efficiently decomposed and treated gas with a low NO emission concentration can be obtained.

[0083] The temperature during the chemical reaction is controlled by, for example, the NH3 concentration, NO concentration, etc. X The concentration and NO concentration can be appropriately set so that they are within the desired ranges. Temperature control can be performed by known methods, for example, by using temperature control means such as a heater, jacket, or heat transfer tube to heat or cool the gas or equipment surrounding the catalyst (hereinafter sometimes referred to as the catalyst layer) or by heating or cooling the gas to be treated flowing into the catalyst layer. Gases emitted from combustion devices such as furnaces and internal combustion engines are often at high temperatures. The inflow of high-temperature gas to be treated easily increases the temperature of the catalyst. Continuous exposure of the catalyst to excessively high temperatures can lead to deterioration of catalytic performance. The temperature of the gas to be treated can be controlled by adding a low-temperature gas such as air to the gas to be treated, or by heat exchange through a partition between the gas to be treated and the heat transfer medium. Treated gas may also be used as the heat transfer medium.

[0084] The process of the present invention preferably includes adding at least one reaction aid selected from the group consisting of ammonia and urea to the gas to be treated. Urea decomposes into carbon dioxide and ammonia through an endothermic reaction. The addition of the reaction aid is performed by removing NO contained in the gas to be treated. X This is preferably done when the amount of N2O is large.

[0085] The amount of reaction aid added to the gas to be treated is determined based on the temperature of the gas to be treated or the treated gas and the NO contained in the gas to be treated or the treated gas. X The addition of a reaction aid to the gas to be treated is preferably adjusted based on the amount of NH3 and N2O. X The amount of NH3 increases in the area where the gas-phase decomposition reactions of NO and N2O are taking place. The increase in the amount of NH3 in the area where the reactions are taking place leads to an increase in the temperature of the catalyst layer and the gas to be treated, while the amount of NH3, NO contained in the treated gas also increases. X and a reduction in the amount of N2O.

[0086] The higher the temperature of the catalyst layer, the faster the direct decomposition reaction of NH3 and the gas-phase decomposition reaction of N2O tend to be. However, the higher the temperature of the catalyst layer, the greater the risk of catalyst deterioration. X The gas phase decomposition reaction of NO and N2O reduces NH3 in the gas to be treated. X The gas-phase decomposition reaction of N2O and the gas-phase decomposition reaction of N2O become difficult to proceed, but the side reaction that produces N2O also becomes difficult to proceed.

[0087] The temperature of the treated gas at each catalyst layer is, for example, preferably 400 to 600° C., more preferably 450 to 550° C. The NO X The concentration of N2O in the final stage treated gas is, for example, preferably 100 ppm or less, more preferably 10 ppm or less.

[0088] Next, examples will be described to demonstrate the effects of the present invention. However, the scope of the present invention is not limited by these examples. Table 6 shows the mass ratio of the first catalyst powder to the second catalyst powder and the Ru / Pt ratio in the catalyst bodies produced in Examples 1 to 18.

[0089] [Example 1: Honeycomb catalyst A] (Preparation of first catalyst powder (1)) A dipping solution of the specified concentration was obtained by adding a chloroplatinic acid solution and a ruthenium nitrate solution to pure water and stirring. This dipping solution was then filled with MFI-type aluminosilicate (pentasil type, pore size = 5.8 Å, cation (nominal cation form) = hydrogen ion, SiO2 / Al2O3 ratio = 24 [mol / mol], specific surface area = 330 m 2 The mixture was stirred to obtain a slurry. The slurry was evaporated to dryness. The resulting dried product was dried at 120°C for at least two hours. The resulting dried product was calcined in air by increasing the temperature from room temperature to 500°C at a rate of 250°C / h, and then maintained at 500°C for two hours. The calcined product was dry-pulverized to obtain a first catalyst powder (1) comprising an MFI-type aluminosilicate loaded with 0.1% by mass of platinum and 5.0% by mass of ruthenium.

[0090] (Preparation of second catalyst powder (1)) Iron nitrate nonahydrate was dissolved in 1 L of ion-exchanged water at 80°C to obtain an aqueous solution of iron nitrate (Fe concentration = 6 mass%) at 80°C. The pH of this aqueous solution of iron nitrate was 1.7. An OSDA-free BEA-type aluminosilicate (SiO / AlO ratio = 12, specific surface area = 370 m) was added to this aqueous solution of iron nitrate. 260 g (dry mass) of ZnO (100%) / g was added and stirred for 2 hours while maintaining the temperature at 80°C, resulting in an ion exchange treatment, yielding a slurry. The slurry was dehydrated using a suction funnel equipped with filter paper. Pure water was poured onto the cake on the filter paper and washed. The washed cake was dried at 120°C for at least 4 hours. The resulting dried product was pulverized. The pulverized product was calcined in air by increasing the temperature from room temperature to 600°C at a rate of 100°C / h, and then maintained at 600°C for 5 hours. The calcined product was dry-pulverized to yield a second catalyst powder (1) consisting of an OSDA-free BEA-type aluminosilicate ion-exchanged with Fe ions.

[0091] (Production of catalyst body) A slurry was obtained by adding 2 parts by mass of the first catalyst powder (1), 98 parts by mass of the second catalyst powder (1), silica sol (OS-1 manufactured by Nissan Chemical Industries, Ltd.) and alumina sol (AS-200 manufactured by Nissan Chemical Industries, Ltd.) to pure water. A cordierite honeycomb substrate (50 cpsi) was immersed in this slurry. The cordierite honeycomb substrate was pulled out of the slurry and subjected to an air blowing treatment to drain the liquid. Next, this was dried at 120°C for 2 hours or more. The obtained dried product was subjected to a firing treatment in air by raising the temperature from room temperature to 500°C at a heating rate of 250°C / h and then maintaining it at 500°C for 2 hours, thereby obtaining a honeycomb catalyst body A. The mass of platinum was 20 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (1) and the second catalyst powder (1).

[0092] (Catalyst Evaluation (1)) The honeycomb catalyst body A was fitted and fixed in the tubular reactor. A simulated gas A containing the components shown in Table 1 was fed into the tubular reactor for SV=10,000 hr -1 The temperature of the tubular reactor was set to 350°C, 400°C, 450°C, or 500°C. X The concentration and N2O concentration were measured, and the NH3 decomposition reaction rate, NO X The by-production rate and N2O by-production rate were calculated using the following formulas. The results are shown in Table 3 and Figures 1 and 2. NH3 decomposition rate = {(Inlet NH3 concentration - Outlet NH3 concentration) - (Inlet NO xConcentration - Outlet NO x Concentration) - 2 / 3 × (Inlet N2O concentration - Outlet N2O concentration)} / {Inlet NH3 concentration - (Inlet NO x Concentration - Outlet NO x Concentration) - 2 / 3 x (Inlet N2O concentration - Outlet N2O concentration)} x 100 NH3 decomposition reaction rate = AV × -Ln (1 - NH3 decomposition rate / 100) NO x By-product rate = exit NO. x Concentration / {(Inlet NH3 concentration - Outlet NH3 concentration) - Inlet NO x Concentration - 2 / 3 x (Inlet N2O concentration - Outlet N2O concentration)} x 100 N2O by-product rate = (Outlet N2O concentration - Inlet N2O concentration) / {(Inlet NH3 concentration - Outlet NH3 concentration) - (Inlet NO x Concentration - Outlet NO x concentration)}×100 AV = gas volume / geometric surface area of ​​honeycomb catalyst body

[0093] [Table 1]

[0094] (Catalyst Evaluation (2)) Simulated gas B containing the components shown in Table 2 was fed into the tubular reactor for SV=10,000 hr -1 The temperature of the tubular reactor was set to 530°C and the reactor was left standing for 70 hours (hydrothermal aging). After that, simulated gas A containing the components shown in Table 1 was introduced into the tubular reactor for SV=10,000 hr -1 The temperature of the tubular reactor was set to 350°C, 400°C, 450°C, or 500°C. X The NH3 decomposition reaction rate and NO concentration were measured in the same manner as in Evaluation (1). X The by-production rate and N2O by-production rate were calculated. The ratio of the NH3 decomposition reaction rate in evaluation (2) to the NH3 decomposition reaction rate in evaluation (1) (aging ratio) was calculated. The results are shown in Tables 4 to 5 and Figures 3 to 8.

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] [Table 5]

[0099] [Table 6]

[0100] [Example 2: Honeycomb catalyst B] (Preparation of first catalyst powder (2)) A first catalyst powder (2) having 0.2 mass % of platinum and 5.0 mass % of ruthenium supported on an MFI-type aluminosilicate was obtained in the same manner as in the preparation of the first catalyst powder (1), except that the amount of chloroplatinic acid aqueous solution added was changed.

[0101] A honeycomb catalyst body B was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (2). The mass of platinum was 40 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (2) and the second catalyst powder (1).

[0102] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst B. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0103] [Example 3: Honeycomb catalyst C] (Preparation of first catalyst powder (3)) A first catalyst powder (3) having 0.5 mass % of platinum and 5.0 mass % of ruthenium supported on an MFI-type aluminosilicate was obtained in the same manner as in the preparation of the first catalyst powder (1), except that the amount of chloroplatinic acid aqueous solution added was changed.

[0104] A honeycomb catalyst body C was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (3). The mass of platinum was 100 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (3) and the second catalyst powder (1).

[0105] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst C. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0106] [Example 4: Honeycomb catalyst body D] (Preparation of first catalyst powder (4)) A first catalyst powder (4) having 1.0 mass % of platinum and 5.0 mass % of ruthenium supported on an MFI-type aluminosilicate was obtained in the same manner as in the preparation of the first catalyst powder (1), except that the amount of chloroplatinic acid aqueous solution added was changed.

[0107] A honeycomb catalyst body D was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (4). The mass of platinum was 200 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (4) and the second catalyst powder (1).

[0108] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst D. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0109] [Example 5: Honeycomb catalyst E] (Preparation of first catalyst powder (5)) A first catalyst powder (5) in which 0.2 mass % of platinum and 5.0 mass % of ruthenium were supported on titanosilicate was obtained in the same manner as in the preparation of the first catalyst powder (2), except that the MFI-type aluminosilicate was changed to titanosilicate (a composite of titania and silica).

[0110] A honeycomb catalyst body E was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (5). The mass of platinum was 40 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (5) and the second catalyst powder (1).

[0111] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst E. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0112] [Example 6: Honeycomb catalyst F] (Preparation of first catalyst powder (6)) A first catalyst powder (6) in which 0.2 mass % of platinum and 5.0 mass % of ruthenium were supported on silica was obtained in the same manner as in the preparation of the first catalyst powder (2), except that the MFI-type aluminosilicate was changed to silica (Si oxide).

[0113] A honeycomb catalyst body F was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (6). The mass of platinum was 40 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (6) and the second catalyst powder (1).

[0114] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst F. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0115] [Example 7: Honeycomb catalyst R] (Preparation of second catalyst powder (2)) OSDA-free BEA-type aluminosilicate (SiO2 / Al2O3 ratio = 12, specific surface area = 370 m 2 / g) was applied to an OSDA-free BEA-type aluminosilicate (SiO2 / Al2O3 ratio = 10, specific surface area = 370 m 2 A second catalyst powder (2) consisting of an OSDA-free BEA-type aluminosilicate ion-exchanged with Fe ions was obtained in the same manner as in the preparation of the second catalyst powder (1), except that the cation exchange rate was changed to (1 / g).

[0116] A honeycomb catalyst body R was obtained in the same manner as in the production of the honeycomb catalyst body B, except that the second catalyst powder (1) was changed to the second catalyst powder (2). The mass of platinum was 40 ppm and the mass of ruthenium was 1000 ppm relative to the total mass of the first catalyst powder (2) and the second catalyst powder (2).

[0117] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst R. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0118] [Example 8: Honeycomb catalyst G] (Preparation of first catalyst powder (a)) An aqueous solution of chloroplatinic acid and cerium nitrate hexahydrate were added to pure water and stirred to obtain an immersion solution of a predetermined concentration. Titanosilicate (a composite of titania and silica) was added to this immersion solution and stirred to obtain a slurry. This slurry was evaporated to dryness. The obtained dried product was dried at 120°C for at least two hours. The obtained dried product was subjected to a calcination treatment in air by raising the temperature from room temperature to 500°C at a rate of 250°C / h and then maintaining it at 500°C for two hours. The obtained calcined product was dry-pulverized to obtain a first catalyst powder (a) consisting of titanosilicate supporting 0.5% by mass of platinum and 2.5% by mass of cerium.

[0119] (Preparation of second catalyst powder (a)) Iron sulfate heptahydrate was dissolved in 1 L of ion-exchanged water at 80°C to obtain an aqueous iron sulfate solution (Fe concentration = 3 mass%) at 80°C. The pH of this aqueous iron sulfate solution was 3.6. A BEA-type aluminosilicate (SiO / AlO ratio = 25 [mol / mol], cation (nominal cation form) = ammonium ion, NaO = 0.05 wt%, specific surface area = 680 m) was added to this aqueous iron sulfate solution. 2 60 g (dry mass) of ammonium hydroxide (NaOH / g) was added and stirred for 2 hours while maintaining the temperature at 80°C, resulting in an ion exchange treatment, yielding a slurry. The slurry was dehydrated using a suction funnel equipped with filter paper. Pure water was poured onto the cake on the filter paper and washed. The washed cake was dried at 120°C for at least 4 hours. The resulting dried product was pulverized. The pulverized product was calcined in air by increasing the temperature from room temperature to 500°C at a rate of 100°C / h, and then maintained at 500°C for 5 hours. The calcined product was dry-pulverized to yield a second catalyst powder (a) consisting of a BEA-type aluminosilicate ion-exchanged with Fe ions.

[0120] (Production of catalyst body) Two parts by mass of the first catalyst powder (a), 98 parts by mass of the second catalyst powder (a), silica sol (OS-1, manufactured by Nissan Chemical Industries, Ltd.), and alumina sol (AS-200, manufactured by Nissan Chemical Industries, Ltd.) were added to pure water to obtain a slurry. A cordierite honeycomb substrate (50 cpsi) was immersed in this slurry. The cordierite honeycomb substrate was removed from the slurry and subjected to an air blowing process to remove the liquid. It was then dried at 120°C for at least two hours. The resulting dried product was calcined in air by increasing the temperature from room temperature to 500°C at a rate of 250°C / h, and then maintained at 500°C for two hours, thereby obtaining a honeycomb catalyst body G. The mass of platinum relative to the total mass of the first catalyst powder (a) and the second catalyst powder (a) was 100 ppm.

[0121] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst G. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0122] [Example 9: Honeycomb catalyst H] (Preparation of first catalyst powder (b)) A first catalyst powder (b) having 1.0 mass % of platinum and 5 mass % of cerium supported on titanosilicate was obtained in the same manner as in the preparation of the first catalyst powder (a), except that the amounts of chloroplatinic acid aqueous solution and cerium nitrate hexahydrate added were changed.

[0123] A honeycomb catalyst body H was obtained in the same manner as in the production of the honeycomb catalyst body A, except that the first catalyst powder (1) was changed to the first catalyst powder (b). The mass of platinum relative to the total mass of the first catalyst powder (b) and the second catalyst powder (1) was 200 ppm.

[0124] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst H. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0125] [Example 10: Honeycomb catalyst body I] (Preparation of first catalyst powder (c)) A first catalyst powder (c) having 0.5 mass% of platinum, 0.5 mass% of ruthenium, and 2.5 mass% of cerium supported on titanosilicate was obtained in the same manner as in the preparation of the first catalyst powder (a), except that an aqueous ruthenium nitrate solution was added to pure water in addition to the aqueous chloroplatinic acid solution and cerium nitrate hexahydrate.

[0126] A honeycomb catalyst body I was obtained in the same manner as in the production of the honeycomb catalyst body G, except that the first catalyst powder (a) was changed to the first catalyst powder (c). The mass of platinum was 100 ppm and the mass of ruthenium was 100 ppm relative to the total mass of the first catalyst powder (c) and the second catalyst powder (a).

[0127] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst I. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0128] [Example 11: Honeycomb catalyst body J] (Preparation of first catalyst powder (d)) A first catalyst powder (d) having 0.05 mass% of platinum and 0.25 mass% of cerium supported on silica was obtained in the same manner as in the preparation of the first catalyst powder (a), except that the amounts of chloroplatinic acid aqueous solution and cerium nitrate hexahydrate added were changed and titanosilicate was replaced with silica.

[0129] Except for changing the first catalyst powder (a) to the first catalyst powder (d), a honeycomb catalyst body J was obtained in the same manner as in the production of the honeycomb catalyst body G. The mass of platinum relative to the total mass of the first catalyst powder (d) and the second catalyst powder (a) was 10 ppm.

[0130] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst J. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0131] [Example 12: Honeycomb catalyst body K] (Preparation of first catalyst powder (e)) A first catalyst powder (e) having 0.25 mass% of platinum and 1.25 mass% of cerium supported on silica was obtained in the same manner as in the preparation of the first catalyst powder (a), except that the amounts of chloroplatinic acid aqueous solution and cerium nitrate hexahydrate added were changed and titanosilicate was replaced with silica.

[0132] A honeycomb catalyst body K was obtained in the same manner as in the production of the honeycomb catalyst body G, except that the first catalyst powder (a) was changed to the first catalyst powder (e). The mass of platinum relative to the total mass of the first catalyst powder (e) and the second catalyst powder (a) was 50 ppm.

[0133] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst K. XThe by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0134] [Example 13: Honeycomb catalyst body L] (Preparation of first catalyst powder (f)) A first catalyst powder (f) having 0.5 mass % of platinum and 2.5 mass % of cerium supported on silica was obtained in the same manner as in the preparation of the first catalyst powder (a), except that the amounts of chloroplatinic acid aqueous solution and cerium nitrate hexahydrate added were changed and titanosilicate was replaced with silica.

[0135] A honeycomb catalyst body L was obtained in the same manner as in the production of the honeycomb catalyst body G, except that the first catalyst powder (a) was changed to the first catalyst powder (f). The mass of platinum relative to the total mass of the first catalyst powder (f) and the second catalyst powder (a) was 100 ppm.

[0136] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst L. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0137] [Example 14: Honeycomb catalyst body M] A honeycomb catalyst body M was obtained in the same manner as in the production of the honeycomb catalyst body J, except that the mass ratio of the first catalyst powder (d) to the second catalyst powder (a) was changed from 2:98 to 20:80. The mass of platinum relative to the total mass of the first catalyst powder (d) and the second catalyst powder (a) was 100 ppm.

[0138] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst M. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0139] [Example 15: Honeycomb catalyst body N] (Preparation of first catalyst powder (g)) A first catalyst powder (g) was obtained in the same manner as in the preparation of the first catalyst powder (a), except that titanosilicate was changed to MOR-type aluminosilicate, and the first catalyst powder (g) had 0.5 mass % of platinum and 2.5 mass % of cerium supported on the MOR-type aluminosilicate.

[0140] Except for changing the first catalyst powder (a) to the first catalyst powder (g), a honeycomb catalyst body N was obtained in the same manner as in the production of the honeycomb catalyst body G. The mass of platinum relative to the total mass of the first catalyst powder (g) and the second catalyst powder (a) was 100 ppm.

[0141] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst N. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0142] [Example 16: Honeycomb catalyst body O] (Preparation of first catalyst powder (h)) A first catalyst powder (h) having 0.5 mass % of platinum and 2.5 mass % of cerium supported on a BEA-type aluminosilicate was obtained in the same manner as in the preparation of the first catalyst powder (a), except that titanosilicate was changed to a BEA-type aluminosilicate.

[0143] A honeycomb catalyst body O was obtained in the same manner as in the production of the honeycomb catalyst body G, except that the first catalyst powder (a) was changed to the first catalyst powder (h). The mass of platinum relative to the total mass of the first catalyst powder (g) and the second catalyst powder (a) was 100 ppm.

[0144] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst O. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0145] [Example 17: Honeycomb catalyst body P] (Preparation of first catalyst powder (i)) A first catalyst powder (i) having 0.25 mass % of platinum and 1.25 mass % of cerium supported on titania was obtained in the same manner as in the preparation of the first catalyst powder (e), except that silica was changed to titania.

[0146] Except for changing the first catalyst powder (a) to the first catalyst powder (i), a honeycomb catalyst body P was obtained in the same manner as in the production of the honeycomb catalyst body G. The mass of platinum relative to the total mass of the first catalyst powder (i) and the second catalyst powder (a) was 50 ppm.

[0147] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst P. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0148] [Example 18: Honeycomb catalyst body Q] (Preparation of first catalyst powder (j)) A first catalyst powder (j) having 0.5 mass % of platinum and 2.5 mass % of cerium supported on titania was obtained in the same manner as in the preparation of the first catalyst powder (f), except that silica was changed to titania.

[0149] Except for changing the first catalyst powder (a) to the first catalyst powder (j), a honeycomb catalyst body Q was obtained in the same manner as in the production of the honeycomb catalyst body G. The mass of platinum relative to the total mass of the first catalyst powder (j) and the second catalyst powder (a) was 100 ppm.

[0150] The NH3 decomposition reaction rate and NO were measured in the same manner as in evaluation (1) and evaluation (2), except that honeycomb catalyst A was replaced with honeycomb catalyst Q. X The by-production rate, N2O by-production rate, and aging rate were calculated. The results are shown in Tables 3 to 5 and Figures 1 to 8.

[0151] The catalyst bodies produced in Examples 1 to 7 had a higher NO by-production rate and NO in both evaluations (1) and (2) than the catalyst bodies produced in Examples 8 to 18. XThe by-product rate is low and the NH3 decomposition reaction rate is high (see Figures 1-2 and Figures 5-6). The catalyst bodies produced in Examples 1-7 have a higher aging rate than the catalyst bodies produced in Examples 8-18 (see Figures 3-4 and Figures 7-8).

[0152] As shown by the above results, the catalyst of the present invention X and / or can promote the gas phase decomposition reaction of ammonia (NH3) while suppressing the by-production of N2O and NO X and / or can promote the gas-phase decomposition reaction of N2O.

Claims

1. a first catalyst powder comprising a support containing at least one selected from the group consisting of ceria, silica, alumina, titania, zirconia, titanosilicate, and aluminosilicate, and ruthenium and platinum supported on the support; a second catalyst powder containing at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; as an active catalyst component, and The first catalyst powder has a platinum content of 0.001 parts by mass or more and less than 1 part by mass per part by mass of ruthenium. Catalyst for gas-phase ammonia decomposition.

2. 2. The catalyst according to claim 1, wherein the first catalyst powder contains 0.01 parts by mass or more and less than 0.5 parts by mass of platinum per 1 part by mass of ruthenium, the amount of platinum contained in 100 parts by mass of the first catalyst powder is 0.01 to 2 parts by mass, and the amount of ruthenium contained in 100 parts by mass of the first catalyst powder is 2 to 10 parts by mass.

3. 2. The catalyst according to claim 1, wherein the first catalyst powder contains platinum in an amount of 0.01 parts by mass or more but less than 0.5 parts by mass per 1 part by mass of ruthenium, the amount of platinum contained in a total of 100 parts by mass of the first catalyst powder and the second catalyst powder is 0.001 to 0.1 parts by mass, and the amount of ruthenium contained in a total of 100 parts by mass of the first catalyst powder and the second catalyst powder is 0.01 to 1 part by mass.

4. 4. The catalyst according to claim 1, 2 or 3, wherein the first catalyst powder has a support containing at least one selected from the group consisting of silica, titanosilicate, MEL-type aluminosilicate and MFI-type aluminosilicate.

5. 4. The catalyst according to claim 1, 2 or 3, wherein the second catalyst powder comprises an iron ion-exchanged BEA-type aluminosilicate.

6. 4. The catalyst of claim 1, 2 or 3, wherein the second catalyst powder comprises an iron ion-exchanged, OSDA-free, BEA-type aluminosilicate.

7. A catalyst body for gas-phase ammonia decomposition, comprising a support and the catalyst according to claim 1, 2 or 3 carried on the support.

8. A catalyst body for gas-phase ammonia decomposition, comprising a molded body containing the catalyst according to claim 1 , 2 or 3 .

9. In the presence of the catalyst according to claim 1, 2 or 3, in a gas to be treated, NH ３ a chemical reaction that converts it into nitrogen and water, NO Ｘ and N ２ The chemical reaction that turns O into nitrogen and water A process that includes:

10. The gas to be treated is continuously passing the second catalyst powder through a first catalyst bed containing, as an active catalyst component, only a second catalyst powder comprising at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; This is followed by successively passing the mixture through a second catalyst layer comprising the catalyst of claim 1, 2 or 3. In the gas to be treated, NH ３ The chemical reaction that turns NO into nitrogen and water Ｘ and N ２ and a process for carrying out a chemical reaction of O to nitrogen and water.

11. The gas to be treated is Continuously passing the mixture through a first catalyst layer containing the catalyst according to claim 1, 2 or 3; and then passing the mixture continuously through a second catalyst layer comprising the catalyst of claim 1, 2 or 3; The proportion of platinum contained in the catalyst placed in the first catalyst layer is lower than the proportion of platinum contained in the catalyst placed in the second catalyst layer. In the gas to be treated, NH ３ The chemical reaction that turns NO into nitrogen and water Ｘ and N ２ and a process for carrying out a chemical reaction of O to nitrogen and water.

12. 10. The process of claim 9, further comprising adding at least one reaction aid selected from the group consisting of ammonia and urea to the gas to be treated.

13. a first catalyst layer comprising a catalyst containing, as an active catalyst component, only a second catalyst powder containing at least one selected from the group consisting of iron ion-exchanged BEA-type aluminosilicate, cobalt ion-exchanged BEA-type aluminosilicate, and copper ion-exchanged BEA-type aluminosilicate; a second catalyst layer comprising the catalyst according to claim 1, 2 or 3, which is disposed downstream of the first catalyst layer; Apparatus for gas phase ammonia decomposition.

14. a first catalyst layer comprising the catalyst according to claim 1, 2 or 3; a second catalyst layer disposed downstream of the first catalyst layer and comprising the catalyst of claim 1, 2 or 3; and The proportion of platinum contained in the catalyst placed in the first catalyst layer is lower than the proportion of platinum contained in the catalyst placed in the second catalyst layer. Apparatus for gas phase ammonia decomposition.

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